Should I not upgrade my resource generators (iron gold food) past level 20-ish?

So all my iron food and gold are level 21-23, so are my smelter, training base, and material workshops. I heard people say that past level 20-ish it’s no longer worth upgrading iron/food/gold and would just focus on the other ones, but I’ve also heard that once season 1 buff comes along it’s worth it to keep upgrading food/iron/gold. So I’m wondering which is it?

My server is like less than a month from starting season 1